Apprentasaurus derives from the words apprentice and dinosaur.
The word "apprentisaurus" is used to describe someone that has been an apprentice for an excessive amount of time, spanning year after year, never graduating to the next level, despite the progression and advancement of his peers.
Thus, the word "dinosaur" comes into play because this individual has been in apprenticeship for such a ridiculous amount of time that it's almost prehistoric!
That guy has been an apprentisaurus for 10 years! And I've been in this trade as long as he has but I've made journeyman already..